The bubbles in champagne, or any sparkling wine, are formed due to a process called carbonation. Carbonation occurs when carbon dioxide (CO2) gas is dissolved in a liquid under pressure. In the case of champagne, the carbonation is a result of a secondary fermentation process that takes place in the bottle.
Champagne is made from a blend of grapes, typically including Chardonnay, Pinot Noir, and Pinot Meunier. After the initial fermentation process, where the grape juice is converted into alcohol, the winemaker adds a mixture of sugar and yeast to the bottle. This triggers a second fermentation, with the yeast consuming the added sugar and producing alcohol and carbon dioxide as byproducts.
However, in a sealed bottle, the carbon dioxide cannot escape into the air and instead dissolves back into the wine, creating the carbonation. The dissolved carbon dioxide remains in the wine until the bottle is opened. When you open a bottle of champagne, the sudden release of pressure causes the carbon dioxide to rapidly escape from the liquid in the form of bubbles, creating the characteristic effervescence and fizziness.
The bubbles rise to the surface of the liquid due to the buoyancy effect and collect at the top, forming a foamy layer. The shape of the glass and the roughness of the glass surface can also influence the formation and release of bubbles, as they provide nucleation sites where bubbles can form and detach from the liquid.
So, the presence of bubbles in champagne is a result of the dissolved carbon dioxide being released when the bottle is opened, creating a delightful and celebratory effervescence that is characteristic of sparkling wines.